Transfer UV maps or Join as UVs?
The operator name from "Join as UV" in 2.66 is the same as the one used in 2.76 for "Transfer UV Maps" - bpy.ops.object.join_uvs() which would indicate that the description has been changed to better describe the function that is performed while the function performed is the same, meaning you should use Transfer UV Maps in a newer version of blender to do the same thing.

In the current release it is described as 


  bpy.ops.object.join_uvs()
  Transfer UV Maps from active to selected objects (needs matching geometry)


While back in 2.66 it was described as


  bpy.ops.object.join_uvs()
  Copy UV Layout to objects with matching geometry


If you also want to compare the source code you will find that the description used in 2.66 and the description used in 2.76 is the only part of the operator that has changed.